Photochromic compounds, a process for their preparation, and their use

ABSTRACT

Compounds of the formula I ##STR1## in which X is O, S, SO, SO 2  or NR 13 , R 13  is, for example, methyl, and R 1  to R 12 , independently of one another, are, for example, H, C 1  -C 12  alkyl, C 1  -C 12  Alkoxy, halogen or --CN. The compounds are photosensitive and photochromic and are suitable as photosensitizers and simultaneously as color indicators, and as photoswitchable color filters.

The present invention relates to photochromic acridones, xanthones, thioxanthones, thioxanthone sulfoxides and thioxanthone sulfodioxides which are substituted in the 1-position by substituted or unsubstituted phenozy, to a process for their preparation, to a photosensitive composition, and to the use of these photochromic comounds as photosensitizers and colour indicators or as photoswitchable colour filters.

It is known that thioxanthones (See U.S. Pat. No. 4,506,083) are photoinitiators or photosensitizers for irradiation-sensitive polymerizable systems. B. K. Manukian, in Helv. Chim. Acta., Vol. 59, Fasc. 7 (1976), pp. 2609 to 2614, described 4-nitroacridones which are 1-substituted by substituted or unsubstituted phenoxy as dyes with good light-fastness properties, DE-A-919 107 describes 1-phenoxy-4-methylxanthen-9-one as an active ingredient for pharmaceuticals.

The prsent invention relates to compounds of the formula I ##STR2## in which X is O, S, SO, SO₂ or NR₁₃, R₁ to R₅, independently of one another, are H, C₁ -C₁₂ alkyl, C₁ -C₁₂ alkoxy, C₁ -C₁₂ alkylthio, C₁ -C₄ alkyl--SO--, C₁ -C₄ alkyl--SO₂ --, halogen, CF₃, --CN, --NO₂, --OH, --COOR₁₄, CON(R₁₅)₂, or --N(R₁₅)₂, or the radical of the formula ##STR3## in which R₁₆ and R₁₇, independently of one another, are C₁ -C₆ alkyl, phenyl, C₁ -C₆ alkylphenyl or (C₁ -C₆ alkyl)₂ -phenyl, or R₃ and R₄ or R₄ and R₅, in each case together, are --CH═CH--CH═CH--, R₆ to R₁₂, independently of one another, are H, C₁ -C₁₂ alkyl, C₁ -C₁₂ alkoxy, C₁ -C₁₂ alkylthio, C₁ -C₁₂ alkyl--SO--, C₁ -C₁₂ alkyl--SO₂ --, benzyl or C₁ -C₄ alk-1-yl which is 1-substituted by a total of one or two --CN and/or --COOR₁₄ C₆ -C₁₀ aryl, C₇ -C₁₄ aralkyl, C₆ -C₁₀ aryl--CO, C₆ -C₁₀ arylthio, C₆ -C₁₀ aryl--SO--, C₆ -C₁₀ aryl--SO₂, C₇ -C₁₄ aralkyloxy, C₇ -C₁₄ aralkylthio, C₇ -C.sub. 14 aralkyl--SO--, C₇ -C₁₄ aralkyl--SO₂ --, C₁ -C₁₈ acyl--O--, --COOR₁₄, --CON(R₁₅)₂, C₁ -C₁₈ acyl--NR₁₅ --, (R₁₅)₂ N--, halogen, --CF₃ or --CN, or each two adjacent radicals of R₆ to R₁₂ are the groups --CO--O--CO-- or --CO--NR₁₃ --CO--, the aryl radicals and radicals containing aryl groups being unsubstituted or substituted by halogen, --CN, --CF₃, C₁ -C₆ alkylthio, C₁ -C₆ alkoxy, C₁ -C₆ alkyl, --COOR₁₄, --CO--N(R₁₅)₂ or C₁ -C₁₂ acyl--O-- R₁₃ is H, C₁ -C₁₂ alkyl or C₁ -C₁₂ acyl, phenyl or benzyl, which are unsubstituted or substituted by C₁ -C₆ alkyl, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, halogen or --COOR₁₄, the two R₁₅ together are C₄ -C₈ alkylene, 3-oxa-1,5-pnetylene, 3-thia-1,5-pentylene, 1,3-butadiene-1,4diyl or 2-aza-1,3-butadiene-1,4-diyl, or the R₁₅ radicals, independently of one another, are H, C₁ -C₁₂ alkyl, or phenyl or benzyl which is unsubstituted or substituted by C₁ -C₆ alkyl, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, halogen or --COOR₁₄, and R₁₄ is H or the radical of an aromatic or aliphatic alcohol minus the OH group, with the exception of 1-phenoxy-4-methylxanthen-9-one.

Alkyl, alkoxy or alkylthio R₁ to R₅ may be linear or branched and preferably contain from 1 to 6, in particular from 1 to 4, carbon atoms. Examples are methyl, ethyl and the isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and the corresponding alkoxy and alkylthio radicals. Preference is given to methyl, ethyl, n- and i-propyl, n-, i- and t-tubyl, methoxy, ethoxy, n- and i-propoxy, n-, i- and t-butoxy, methylthio and ethylthio. C₁ -C₄ Alkyl--SO-- or C₁ -C₄ alkyl--SO₂ -- R₁ to R₅ may be, for example, methyl-, ethyl-, n-propyl- or n-butylsulfinyl or -sulfonyl.

Halogen R₁ to R₅ may be, for example, --F, --Cl, --Vr or --I.

--COOR₁₄ R₁ to R₅ are preferably --COO--C₁ -C₁₈ alkyl; --N(R₁₅)₂ R₁ to R₅ are preferably --N(C₁ -C₆ alkyl)₂ ; and --CON(R₁₅)₂ R₁ to R₅ are preferably --CO--N(C₁ -C₆ alkyl)₂ or --CO--NH(C₁ -C₆ alkyl).

R₁₆ and R₁₇ are preferably methyl, ethyl, phenyl, methylphenyl or dimethylphenyl.

In a preferred embodiment, R₁ to R₅, independently or one another, are H, C₁ -C₆ alkyl, C₁ -C₆ alkoxy, halogen, --CF₃, --CN, --NO₂, --COOR₁₄, --OH, --N(R₁₅)₂ or R₃ and R₄ or R₄ and R₅, in each case together are --CH═CH--CH═CH--, where R₁₄ is linear or branched C₁ -C₁₈ alkyl, and each R₁₅ is C₁ -C₆ alkyl.

In another preferred embodiment, at least 2, in particular at least 3, of the radicals R₁ to R₅ are H.

Alkyl, alkoxy, alkylthio, alkyl--SO-- or alkyl--SO₂ -- R₆ to R₁₂ preferably contain from 1 to 6, in particular from 1 to 4, carbon atoms. Examples and further preferences are as given above for R₁ to R₅.

R₆ to R₁₂ as C₁ -C₄ alk-1-yl or benzyl which is 1-substituted by a total of one or two --CN and/or --COOR₁₄ may be, for example, cyanomethyl, dicyanomethyl, α-cyanobenzyl, 1-cyanoeth-1-yl, 1,1-dicyanoeth-1-yl, (methoxycarbonyl)methyl, (ethoxycarbonyl)methyl, di(methoxycarbonyl)methyl, α-(methoxycarbonyl)benzyl, 1,1-di(methoxycarbonyl)-eth-1-yl or cyano-(methoxycarbonyl)-methyl.

Aryl R₆ to R₁₂ are preferably naphthyl and in particular phenyl. R₆ to R₁₂ as radicals conaining aryl groups preferably contain naphthyl and in particular phenyl groups.

Aralkyl R₆ to R₁₂ are preferably phenyl(C₁ -C₄ alkyl), in particular benzyl or 1-phenyleth-1-yl or -2-yl.

Aryl-CO-- R₆ to R₁₂ are preferably naphthyl--CO-- and in particularphenyl--CO--.

Aryloxy R₆ to R₁₂ are preferably naphthyloxy and in particular phenoxy.

Arylthio R₆ to R₁₂ are in particular naphthylthio or phenylthio.

Aryl--SO-- or aryl--SO₂ R₆ to R₁₂ are preferably phenyl--SO-- or phenyl--SO₂ --.

Aralkoxy R₆ to R₁₂ are preferably phenyl(C₁ -C₄ alkyl--O--, in particular benzyloxy.

Aralkylthio R₆ to R₁₂ are preferably phenyl(C₁ -C.sub. alkyl--S--, in particular benzylthio.

Aralkyl--SO-- R₆ to R₁₂ are preferably phenyl(C₁ -C₄ alkyl--SO--, in particular benzyl--SO--.

Aralkyl--SO₂ -- R₆ to R₁₂ are preferably phenyl (C₁ -C₄ alkyl--SO₂ --, in particular benzyl--SO₂ --.

C₁ -C₁₈ Acyl--O-- R₆ to R₁₂ preferably conform to the formula R₁₉ --CO--O, in which R₁₉ is H or C₁ -C₁₇ alkyl, C₂ -C₁₇ alkenyl, C₃ -C₈ cycloalkyl, C₆ -C₁₀ aryl or C₇ -C₁₄ aralkyl, each of which is unsubstituted or substituted by halogen, preferably --F or --Cl, --OH, C₁ C₆ alkoxy or C₁ -C₆ alkylthio. R₁₉ is preferably C₁ -C₁₂ alkyl, C₂ -C₁₂ alkenyl, cyclopentyl, cyclohexyl, phenyl or benzyl.

If R₆ to R₁₂ are the group --COOR₁₄, r₁₄ is in particular C₁ -C₁₈ alkyl.

If R₆ to R₁₂ are the group --CON(R₁₅)₂ or the group --CONHR₁₅, R₁₅ are in particular C₁ -C₆ alkyl.

If R₆ to R₁₂ are the group C₁ -C₁₈ acyl--NR₁₅ --, the group preferably conforms to the formula R₁₉ --CO--NR₁₅ --, in which R₁₉ is as defined for the group R₁₉ --CO--O--, including the preferences, and R₁₅ is preferably H or C₁ -C₆ alkyl.

If R₆ to R₁₂ are the group --N(R₁₅)₂, each R₁₅ is preferably C₁ -C₆ alkyl, cyclohexyl, phenyl, benzyl, tetramethylene, pentamethylene, 3-oxa-1,5-pentylene or --CH═CH--CH═CH--.

Halogen R₆ to R₁₂ are preferably --F, --Cl or --Br.

If R₆ to R₁₂ are aryl groups or radicals containing aryl groups, these may be unsubstituted, monosubstituted or polysubstituted, preferably monosubstituted or disubstituted, by halogne, preferably --F, --Cl or --Br, --CN, --OH, --CF₃, C₁ -C₆ alkylthio (for example methylthio or ethylthio), C₁ -C₆ alkoxy (for example methoxy, ethoxy, n- or i-propoxy, n-, i- or t-butoxy), C₁ -C₆ alkyl (for example methyl, ethyl, n- or i-propyl, n-, i- or t-butyl), --COOR₁₄, in which R₁₄ is preferably H or C₁ -C₁₂ alkl, --CON(R₁₅)₂, in which R₁₅ is preferably H or C₁ -C₆ alkyl, or C₁ -C₁₂ acyl--O--, preferably C₁ -C₁₁ alkyl--CO--O--.

Alkyl R₁₃ preferably contains from 1 to 6, in particuar from 1 to 4, carbon atoms and is, for example, methyl or ethyl. Acyl R₁₃ is preferably R₁₉ --CO--, in which R₁₉ is as defined above and is in particular C₁ -C₈ alkyl, cyclohexyl, phenyl or benzyl.

An alcohol radical R₁₄ preferably contains from 1 to 30, in particular from 1 to 20, especially from 1 to 10, carbon atoms. An aromatic alcohol radical R₁₄ may be C₆ -C₁₀ aryl, in particular phenyl or phenyl(C₁ -C₄ alkyl), in particular benzyl or 1-phenyleth-2-yl, which may be substituted by 1 or 2 C₁ -C₁₈ alkyl, in particular C₁ -C₁₂ alkyl groups.

An aliphatic radical R₁₄ may be an open-chain or cyclic radical, e.g. C₁ -C₂₀ alkyl, in particular C₁ -C₁₈ alkyl, especially C₁ -C₁₂ alkyl; C₃ -C₈ cycloalkyl or C₃ -C₈ cycloalkylmethyl, in particular cyclopentyl, cyclohexyl or cyclohexylmethyl.

R₁₄ may alternatively be a polyoxaalkylene radical of the formula --C_(n) H_(2n) --O_(m) R₁₈ in which n is an integer from 2 to 6, in particular from 2 to 4, especially 2 or 3, and m is a number from 1 to 20, in particular 1 to 12, especially 1 to 6, and R₁₈ is H, C₁ -C₁₈ alkyl, in particular C₁ -C₁₂ alkyl, especially C₁ -C₆ alkyl, C₃ -C₈ cycloalkyl, in particular C₅ - or C₆ cycloalkyl or -cycloalkylmethyl; or phenyl or benzyl, which may be substituted by 1 or 2 alkyl groups having from 1 to 12, in particular from 1 to 6, carbon atoms.

Alkyl R₁₅ preferably contains from 1 to 5, in particular from 1 to 4, carbon atoms and is in particular methyl or ethyl. Substituted phenyl or benzyl R₁₅ preferably contains 1 or 2 substituents. Halogen and --COOR₁₄ as substituents are preferably --F, --Cl, --Br, --COOH and --COO(C₁ -C₁₂ alkyl). The two R₁₅ radicals together, as alkylene, are preferably tetramehtylene or pentamethylene.

In a preferred embodiment, at least 2, in particular at least 3 and especially at least 4, of the radicals R₆ to R₁₂ are H.

A preferred subgroup of compounds of the formula I comprises those in which R₆ to R₁₂, independently of one another, are H, C₁ -C₆ alkyl, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, C₁ -C₆ alkyl--SO--, C₁ -C₆ alkyl--SO₂, C₁ - or C₂ alkyl which is 1-substituted by a total of one or 2 --CN and/or COOR₁₄, phenyl, pneyly-C₁ -C₄ alkyl, pnehyl--CO--, phenyloxy, phenylthio, phenyl--SO--, phenyl--SO₂ --, benzyloxy, benzylthio, benzyl--SO--, benzyl--SO--, C₁ -C₈ acyl--NR₁₅ --, --COOR₁₄, --CON(R₁₅)₂, (R₁₅)₂ N--, --F, --Cl, --Br, --CF₃ or --CN or each two adjacent R₆ to R₁₂ radicals together are --CO--O--CO-- or --CO--NR₁₃ --CO--, R₁₃ is C₁ -C₆ alkyl, or phenyl or benzyl which are unsubstituted or substituted by C₁ -C₄ alkyl, C₁ -C₄ alkoxy, F, C, Br or --COOR₁₄, R₁₄ is H, linear or branched C₁ -C₁₈ alkyl, phenyl, benzyl or --C_(n) H_(2n) --O_(m) R₁₈, where n is an integer from 2 to 6, and m is a number from 1 to 20, and R₁₈ is H, C₁ -C₁₈ alkyl, cyclohexyl, phenyl or benzyl, and R₁₅ is C₁ -C₆ alkyl, or phenyl or benzyl which is unsubstituted or substituted by C₁ -C₄ alkyl, C₁ -C₄ alkoxy, --F, --Cl, --Br or --COOR₁₄, or the two R₁₅ radicals together are 1,4-butylene, 1,5-pentylene, 3-oxa-1,5-pentylene or 1,3-butadiene-1,4-diyl.

Preferred groups of compounds are also those in which, in the formula I, R₆ is H, --Cl, --Br or methyl, or in which, in the formula I, R₉ is H or --Cl, or in which, in the formula I, R₁₁ is H or --Cl, or in which, in the formula I R₁₀ and/or R₁₂ is --Cl, --Br, unsubstituted or substituted phenoxy or --COO--(C₁ -C₁₂ alkyl), or in which, in the formula I, R₇ and/or R₈ is H, --F, --Cl, --CF₃, --Br, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, phenyl--CO--, α-cyanobenzyl, C₁ -C₈ acyl--NR₁₅ --, pyrryl, --COO--(C₁ -C₁₂ alkyl), or phenoxy, phenylthio or phenylsulfonyl, which are unsubstituted or substituted by --F, --Cl, C₁ -C₄ alkoxy, --COOH or --COO--(C₁ -C₁₂ alkyl), or R₇ and R₈ together are ##STR4## and R₁₃ is H or C₁ -C₆ alkyl, or in which in the formula I, R₁₃ is C₁ -C₄ alkyl or C₁ -C₈ acyl, or phenyl or benzyl which are unsubstituted or substituted by F or --COOR₁₄, and R₁₄ is H or C₁ -C₁₂ alkyl, or in which, in the formula I, R₁₄ is H, C₁ -C₁₈ alkyl, --C_(n) H_(2n) --O_(m) H, phenyl, C₁ -C₆ alkylphenyl, benzyl, C₁ -C₆ alkylbenzyl or cyclohexyl, n is an integer from 1 to 6, and m is a number from 1 to 20, or in which, in the formula I, R₁₅ is H, C₁ -C₆ alkyl, phenyl, benzyl, or the two R₁₅ radicals together are tetramethylene, pentamethylene, 3-oxa-1,5-pentylene or 1,3-butadiene-1,4diyl.

Particularly preferred compounds of the formula I are those in which R₁ to R₅ are H or R₁, R₂, R₄ and R₅ are H and R₃ is --CO₂ C₂ H₅, R₆ and R₈ are Cl, and R₇ and R₉ -R₁₂ are H, and X is NCH₃ or N-n-C₃ H₇.

The compounds according to the invention can be obtained in a manner known per se by nucleophilic substitution of 1-nitro- or 1-haloxanthones, -thioxanthones, -thioxanthone sulfoxides, -thioxanthone sulfodioxides or -acridones by phenol salts. The invention furthermore relates to a process for the preparation of compounds of the formula I which comprises reacting a compound of the formula II ##STR5## in which X and R₆ to R₁₂ are as defined in claim 1, and Y is --NO₂ or halogen, with a compound of the formula III ##STR6## in which R₁ to R₅ are as defined in claim 1, and M⊕ is an alkali metal cation, or a quaternary ammonium or phonphonium cation, at elevated temperature in the presence of a dipolar aprotic or protic solvent.

The process according to the invention is preferably carried out at temperatures of from 50 to 200° C., in particular from 50 to 150° C. The salts of the formula III can be employed as such or produced in situ in the reaction mixture by reacting an appropriate phenol with an alkali metal, ammonium or phosphonium base. The salts of the formula III can be employed in equimolar amounts or in excess, e.g. an excess of up to 40 mol-%.

Examples of suitable solvents are N-substituted carboxamides and lactams (for example dimethylformamide of N-methylpyrrolidone), sulfoxides and sulfones (for example dimethyl sulfoxide or tatramethylene sulfone) or ethers (for example di-n-propyl ether, di-n-butyl ether, tetrahydrofuran or dioxane).

The compounds of the formula I are isolated and purified by conventional method, for example by crystallization and recrystallization, or by chromatography.

The compounds of the formula III are known or can be obtained in a known manner by reacting appropriate phenols with alkali metal, ammonium or phosphonium bases. Particularly suitable alkali metal cations are Liα, Na⊕ and K⊕; and examples of particularly suitable quaternary onium cations are (C₁ -C₆ alkyl)₄ N⊕, (C₁ -C₆ alkyl)P⊕ or tetraphenylphosphonium.

Compounds of the formula I containing functional groups, for example --COOH or --NH₂, can be derivatized in a known manner to give esters or amides.

Some of the compounds of the formula II in which Y, as halogen, is preferably --F, --Cl or --Br are known or can be prepared by processes known per se by intramolecular Friedel-Crafts acylation (thioxanthones, see, for example U.S. Pat. No. 4,385,182 or F. Mayer, Chem. Ber. 43, pp. 584 ff (1910); xanthones, see, for example, F. Ullmann et al., Chem. Ber. 38 pp. 2120 ff (1905); acridones, see for example, C. W. Renocastle et al., Synthesis 1985, pp. 21 ff). Thioxanthone sulfoxides and sulfodioxides can also be obtained by oxidation of the thioxanthones.

Compounds of the formula I are heat resistant, colourless to slightly yellow and predominantly crystalline and are soluble in organic solvent. They are highly effective photoinitiators and photosensitizers for photopolymerizable or photodimerizable systems which contain ethylenically unsaturated double bonds.

When the compounds are irradiated, alone or in a substrate, with light having a wavelength of from about 300 to 450 nm, a pronounced colour change to blue/violet is surprisingly found. This colour change is irreversible.

The compounds of the formula I can therefore be used as photoinitiators and in particular as photosensitizers in photopolymerizable systems, with a simultaneous action as colour indicators. It is thus possible to mark exposed products (for example protective coatings, printing plates, offset printing circuits, solder stop masks) and to differentiate them from unexposed products, and furthermore to separate out products which have been exposed incorrectly, during product monitoring or after development.

The substantial advantage when used as colour indicators is the increase in the sensitizer action. Additives usually employed as colour-change systems cause a reduction in photosensitivity.

The compounds of the formula I can also be used as such, in solution or incorporated into polymers as colour photoindicators or as photoswitching elements.

The invention furthermore relates to a radiation-sensitive composition containing

a) a radiation-sensitive organic material, and

b) at least one compound of the formula I, including 1-phenoxy-4-methylxanthen-9-one.

The compounds of the formula I can be present in an amount of from 0.001 to 20% by weight, in particular from 0.001 to 10% by weight, especially from 0.01 to 5% by weight, based on component a).

Radiation-sensitive and thus also photostructurable materials are known. They may be positive or negative systems. Such materials are described, for example, by G. E. Green et al., in J. Macro. Sci. Revs. Macr. Chem., C21)2), 187-273 ( (1981-82) and by G. A. Delzenne in Adv. Photochem., 11, pp. 1-103 (1979).

The radiation-sensitive organic material is preferably a1) a nonvolatile monomeric, oligomeric or polymeric substance containing photopolymerizable or photodimerizable, ethylenically unsaturaged groups, a2) a cationically curable system of a3) photocrisslinkable polyimides.

Examples of photopolymerizable substances are acrylates and in particular methacrylates of polyols, e.g. ethylene glycol, propanediol, butanediol, hexanediol, di(hydroxymethyl)cyclohexane, 2,2-bis(4-hydroxyethoxyphenyl)propane, polyoxyalkylenediols, for example di-, tri- or tetraethylene glycol, di- or tri-1,2-propylene glycol, trimethylolmethane, -ethane or -propane and pentaerythritol, which can be used alone, in mixtures and blended with binders. Products of the addition of acrylic acid and in particular methacrylic acid onto bisglycidyloxy compounds, for example 2,2-bis(4-glycidyloxyphenyl)propane, are also suitable. Methylenebisacrylamide is furthermore suitable.

Examples of photodimerizable substances are homopolymers and copolymers which contain cinnamic acid groups or substituted maleinimidyl compounds in side groups or chalcone groups in the polymer chain.

Preferred compositions of this type are those in which component a1) is a homopolymer or copolymer of acrylates, methacrylates or maleates whose ester groups contain a radical of the formula ##STR7## in which A is unsubstituted or hydroxyl-substituted, linear or branched C₂ -C₁₂ alkylene, cyclohexylene orphenylene, and R₂₀ and R₂₁, independently of one another, are Cl, Br, phenyl or C₁ -C₄ alkyl, or R₂₀ and R₂₁ together are trimethylene, tetramethylene or ##STR8##

Polymers of this type are described, for example, in U.S. Pat. No. 4,193,927.

The photopolymerizable or photodimerizable substances may contain further additives which are customary for processing or application and in addition other photoinitiators or photosensitizers.

The cationically curable systems are preferably epoxide compounds containing at least two epoxide groups in the molecule and mixed with a photoinitiator. Examples of suitable photoinitiators are metallocenes, metallocene carbonyls and onium salts, which are described, for example, in the abovementioned publications. The curable systems may contain additives which are customary for processing and application.

Photosensitive polyimides are described, for example, in DE-A-1, 962 588, EP-A-0 132 221, EP-A-0 134 752, EP-A-0 162 017, EP-A-0 181 837 and EP-A-0 182 745.

The composition according to the invention is applied as a coating to substrates by known methods, and either a protective coating is produced by irradiation over the entire area or a relief image is produced by irradiation under a photomask with subsequent development.

The invention furthermore relates to a composition containing a) a colourless, organic solvent, a polymer or an organic glass or a composite glass, and b) a compound of the formula I, including 1-phenoxy-4-methylxanthen-9-one. Component b) is preferably present in an amount of from 0.001 to 20% by weight, in particular from 0.001 to 10% by weight, especially from 0.01 to 5% by weight based on component a). Organic solutions can be used to coat other substances, e.g. inorganic glasses, which can then be used as photoswitchable substrates. The compounds of the formula I can also be sublimed onto substrates. The coated substartes can be provided with a protective coating of, for example, transparent polymers. Examples of suitable solvents are hydrocarbons, halogenated hydrocarbons, ketones, carboxylic acid esters and lactones, N-alkylated acid amides and lactams, alkanols and ethers.

Examples of suitable polymers are thermosets, thermoplastics and structurally crosslinked polymers. The polymers are preferably transparent. Such polymers and organic glasses are known to those skilled in the art. The compounds according to the invention are incorporated by conventional methods, e.g. by dissolution and removal of the solvent, calendering or extrusion. The compounds according to the invention can also be incorporated into the substrates before, during or after preparation.

The invention furthermore relates to a process for the production of coloured materials under the action of light, which comprises incorporating a compound of the formula I, includign 1-phenoxy-4-methylxanthen-9-one, into the material and then irradiating the material with light.

The invention furthermore relates to the use of compounds of the formula I, including 1-phenoxy-4-methylxanthen-9-one, as photosensitizers and colour indicators or photoswitching elements under the action of light.

The examples below illustrate the invention in greater detail.

A) PREPARATION EXAMPLES Examples A1-A76

16 mmol of 1-haloxanthone, -thioxanthone or -acridone, 24 mmol of phenol, 40 mmol of potassium carbonate and 45 ml of solvent are warmed with stirring. The reactio mixture is poured into 200 ml of ice, and the precipitate is filtered off and dissolved in toluene/tetrahydrofuran (1:1). The solution is washed successively with 5% strength NaOH, water and saturated aqueous sodium chloride solution, and dried using sodium sulfate. The solvent is removed by distillation, and the residue is recrystallized from toluene/isopropanol (1:1).

Further details are given tin Tables 1a and 1b. The data relate to the formula ##STR9##

    TABLE 1a       No. A X R R.sub.6 R.sub.7 R.sub.8 R.sub.9 R.sub.10 R.sub.11 R.sub.12      Melting point (°C.)         1 O Ph H OPh H H H H Cl 168-176  2 O Ph H OPh H H H H OPh 181-183  3      O Ph H OPh H Cl OPh Cl CO.sub.2 C.sub.2 H.sub.5 195-197  4 O Ph H Cl H H      H H Cl 152-154  5 O Ph H Cl H Cl Cl Cl CO.sub.2 C.sub.2 H.sub.5 229-231      6 N-3,5-F.sub.2 Ph Ph H F H H H H H  7 NC.sub.2 H.sub.5 Ph H Cl H H H H      H 189-191  8 NCH.sub.2 Ph Ph H F H H H H H 223-225  9 NCH.sub.3 Ph H OPh      H H H H H 100-105 10 NCH.sub.3 Ph H H H H H H CF.sub.3 142-145 11      N-2-COOHPh Ph H Cl H H H H H <260 12 NC.sub.2 H.sub.5 3-BrPh H Cl H H H      H H 183-187 13 NC.sub.2 H.sub.5 4-ClPh H Cl H H H H H 147-148 14      NC.sub.2 H.sub.5 Ph H PhO H H H H H 164-65  15 NC.sub.2 H.sub.5 3-BrPh H      3-BrPhO H H H H H 126-129 16 NCH.sub.3 Ph H H Cl H H H H 129-130 17      NC.sub.2 H.sub.5 3,5-(CH.sub.3 O).sub.2 Ph H 3,5-(CH.sub.3 O).sub.2 PhO      H H H H H 152-154 18 NC.sub.2 H.sub.5 3,5-(CH.sub.3 O).sub.2 Ph H Cl H H      H H H 180-183 19 NC.sub.2 H.sub.5 4-ClPh H 4-ClPhO H H H H H 148-149 20      NC.sub.2 H.sub.5 4-(oct-2-yl-O.sub.2 C)Ph H Cl H H H H H Oil 21 NC.sub.2      H.sub.5 4-(oct-2-yl-O.sub.2 C)Ph H 4-(oct-2-yl-O.sub.2 C)PhO H H H H H      Oil 22 NC.sub.2 H.sub.5 4-(C.sub.2 H.sub.5 O.sub.2 C)Ph H Cl H H H H H      138-140 23 Ni-propyl Ph H Cl H H H H H 143-145       24       Ph H Cl H H H H H 144-147       25      ##STR10##       Ph H OPh H H H H H 60-70       26      ##STR11##       Ph H Cl H H H H H 102-104       27      ##STR12##       Ph H OPh H H H H H 102-105  28 NC.sub.2 H.sub.5 Ph H Cl H H H H H      128-130 29 NCH.sub.3 Ph Cl H Cl H H H H 173-174 30 NC.sub.3 H.sub.7 Ph      Cl H Cl H H H H 116-118 31 S Ph Cl Cl Cl H H H H 190-192 32 S Ph Cl PhO      Cl H H H H 203-204 33 S Ph Br H F H H H H 199-202 34 S Ph H H CH.sub.3 O      H H H H 191-193 35 S Ph Cl H Cl H H H H 183-185 36 S 4-NO.sub.2Ph Cl H      Cl H H H H 228-230 37 S 4-FPh Cl H Cl H H H H 149-150 38 S 4-BrPh Cl H      Cl H H H H 217-219 39 S 4-ClPh Cl H Cl H H H H 192-195 40 S 4-IPh Cl H      Cl H H H H 236-238 41 S 4-CH.sub.3Ph Cl H Cl H H H H 175-177 42 S      4-CH.sub.3 OPh Cl H Cl H H H H 153-155 43 S (C.sub.2 H.sub.5).sub.2 NPh      Cl H Cl H H H H 134-135 44 S 3-ClPh Cl H Cl H H H H 150-152 45 S      3-CH.sub.3 OPh Cl H Cl H H H H 169-171 46 S 3,5-(CH.sub.3 O).sub.2 -Ph      Cl H Cl H H H H 192-194 47 S 2,4-Cl.sub.2Ph Cl H Cl H H H H 235-237 48 S      3-BrPr Cl H Cl H H H H 172- 174 49 S 3,4-Cl.sub.2Ph Cl H Cl H H H H      187-188 50 S Ph Cl H Cl H H CO.sub.2 C.sub.2 H.sub.5 H 178-183 51 S      4-CNPh Cl H Cl H H H H 248-251 52 S 4-(C.sub.2 H.sub.5 O.sub.2 C)-Ph Cl      H Cl H H H H 172-174 53 S 4-t-ocytl-Ph Cl H Cl H H H H 137-139 54 S      4-(n-C.sub.12 H.sub.25 O.sub.2 C)-Ph Cl H Cl H H H H 109-112 55 S Ph Cl      H Cl H C.sub.2 H.sub.5 O.sub.2 C H H 170-173 56 S Ph CH.sub.3 H CH.sub.3      H H H C.sub.2 H.sub.5 O.sub.2 C 153-155 57 S 4-(n-C.sub.12 H.sub.25      O.sub.2 C)-Ph Cl H Cl H C.sub.2 H.sub.5 O.sub.2 C H H 129-133 58 S      3-(C.sub.2 H.sub.5 O.sub.2       C)-Ph Cl H Cl H H H H 163-165 59 S 3-CF.sub.3Ph Cl H Cl H H H H 167-169      60 S Ph Cl H Cl H H H C.sub.2 H.sub.5 O.sub.2 C 168-170  61 S Ph Cl H Cl      H H H       ##STR13##       127-129  62 S 4-(n-C.sub.12 H.sub.25 O.sub.2 C)-Ph Cl H Cl H H H       ##STR14##       Oil  63 S 1-naphthyl Cl H Cl H H H H 247-249 64 S 2-naphthyl Cl H Cl H      H H H 197-200 65 S 3-OH-4-R'Ph Cl H Cl H H H H 235-238 66 S Ph H Cl H H      H H H 114-116 67 S Ph H PhO H H H H H 151-153 68 S 2,4-Cl.sub.2Ph H Cl H      H H H H 205-208 69 S 3,5-Cl.sub.2Ph H Cl H H H H H 195-197 70 S 3,5-Cl.su      b.2Ph H 3,5-Cl.sub.2Ph H H H H H 202-204 71 S 3,5-Cl.sub.2Ph Cl H Cl H H      H H 214-218 72 S Ph H Cl Cl H H H H 162-165 73 S 3-CH.sub.3 OPh H Cl H H      H H H 102-104 74 S 3-CH.sub.3       OPh Cl Cl Cl H H H H 172-174 75 S 3-CH.sub.3 OPh Cl 3-CH.sub.3 OPh Cl H      H H H -- 76 S Ph Br H Br H H H H 174-176

                  TABLE 1b                                                         ______________________________________                                                                  Reaction                                                                       temperature                                                                             Reaction                                                                              Yield                                 No. A 1-Halogen Solvent  (°C.)                                                                            time (h)                                                                              (%)                                   ______________________________________                                          1    Cl        DMSO     120      19      4                                     2    Cl        DMSO     120      19      7                                     3    Cl        DMSO     120      18     53                                     4    Cl        Bu.sub.2 O                                                                              120      23     52                                     5    Cl        Bu.sub.2 O                                                                              130      21     44                                     6    F         Dioxane  100       3     33                                     7    Cl        Bu.sub.2 O                                                                              150      72     84                                     8    F         Dioxane  100       4     76                                     9    Cl        DMSO     120       2     78                                    10    F         DMSO     100      36     45                                    11    Cl        DMSO     130      18     58                                    12    Cl        Bu.sub.2 O                                                                              140      24     72                                    13    Cl        Bu.sub.2 O                                                                              140      16     66                                    14    Cl        DMSO     140      23     80                                    15    Cl        DMSO     140      23     75                                    16    Cl        DMSO     130      24     71                                    17    Cl        DMSO     140      18     52                                    18    Cl        Bu.sub.2 O                                                                              140      64     24                                    19    Cl        DMSO     140      19     72                                    20    Cl        Bu.sub.2 O                                                                              140      40     95                                    21    Cl        DMSO     140      61     54                                    22    Cl        Bu.sub.2 O                                                                              140      42     31                                    23    Cl        DMSO     140      45     64                                    24    Cl        Bu.sub.2 O                                                                              140      5 days 21                                    25    Cl        Bu.sub.2 O                                                                              140      5 days 15                                    26    Cl        Bu.sub.2 O                                                                              140      68     61                                    27    Cl        Bu.sub.2 O                                                                              140      68      8                                    28    Cl        Bu.sub.2 O                                                                              140      69     53                                    29    Cl        NMP      100      18     93                                    30    Cl        DMSO     110       3     83                                    31    Cl        Dioxane  120      24     44                                    32    Cl        Dioxane  120      24     13                                    33    F         Bu.sub.2 O                                                                              130      17     75                                    34    F         DMSO     130       9     36                                    35    Cl        DMSO      90      23     58                                    36    Cl        DMSO     120      23     17                                    37    Cl        DMSO      90      23     58                                    38    Cl        DMSO      80      28     55                                    39    Cl        DMSO      80      28     51                                    40    Cl        DMSO      80      17     48                                    41    Cl        DMSO      80      17     58                                    42    Cl        DMSO      80      19     65                                    43    Cl        DMSO     100      20     34                                    44    Cl        DMSO      80      21     61                                    45    Cl        DMSO     100       6     55                                    46    Cl        DMSO     100      18     64                                    47    Cl        DMSO     120      24     47                                    48    Cl        DMSO      80      18     60                                    49    Cl        DMSO     100      18     56                                    50    Cl        DMSO      80       3     70                                    51    Cl        DMSO     100      19     58                                    52    Cl        DMSO     100      15     61                                    53    Cl        DMSO      80      16     53                                    54    Cl        DMSO     100      18     49                                    55    Cl        DMSO      80      18     55                                    56    Br        DMSO     140      32      3                                    57    Cl        DMSO      90      22     57                                    58    Cl        DMSO      80      22     56                                    59    Cl        DMSO      90       6     61                                    60    Cl        DMSO      80      16     67                                    61    Cl        DMSO      80       6     65                                    62    Cl        DMSO     100       6     88                                    63    Cl        DMSO     100      22     52                                    64    Cl        DMSO     100      22     58                                    65    Cl        DMSO     100      18     73                                    66    Cl        Dioxane  100      47     63                                    67    Cl        DMSO     120      20     97                                    68    Cl        Dioxane  100      72     27                                    69    Cl        Dioxane  100      72     80                                    70    Cl        DMSO     120      18     70                                    71    Cl        DMSO     100       3     46                                    72    Cl        Bu.sub.2 O                                                                              130      96     42                                    73    Cl        Dioxane  100      72     52                                    74    Cl        Bu.sub.2 O                                                                              140       7     80                                    75    Cl        --       --       --      .sup. 4.sup.1)                       76    Br        Bu.sub.2 O                                                                              140      20     69                                    ______________________________________                                          Abbreviations:                                                                 DMSO: Dimethyl sulfoxide                                                       Bu.sub.2 O: Di(n-butyl) ether                                                  NMP: Nmethylpyrrolidone                                                        Ph: Phenyl                                                                     ##STR15##                                                                      .sup.1) Byproduct from Example A74                                       

Examples A77-A82

340 mg (1 mmol) 3-chloro-1-phenoxythioxanthone, 3 ml (75 mmol) of methanol and 420 mg (3 mmol) of potassium carbonate are heated at 110° C. for 24 hours in 5 ml of dimethyl sulfoxide. The reaction mixture is poured into water and neutralized using dilute hydrochloric acid, and the product is extracted with toluene/tetrahydrofuran. The organic phase is washed with saturated aqueous sodium bicarbonate solution, dried using sodium sulfate and evaporated. The residue is purified by chromatography (silica gel, hexane/ethyl acetate 10:1) and subsequently recrystallized from toluene. Yield: 113 mg (34%), melting point 154-156° C.

The following compounds (Table 2) are prepared analogously using sodium phenylsulfinate, thiophenol, sodium methylmercaptide or thiosalicylic acid:

    __________________________________________________________________________     Example                          Yield                                                                              Melting                                   No. A                                                                               X R R.sub.6                                                                          R.sub.7  R.sub.8                                                                          R.sub.9                                                                          R.sub.10                                                                          R.sub.11                                                                          R.sub.12                                                                          (%) point (°C.)                        __________________________________________________________________________     78   S Ph                                                                               H SO.sub.2 Ph                                                                             H H H  H  H  80  201-204                                   79   S Ph                                                                               H SPh      H H H  H  H  78    161-163.5                               80   S Ph                                                                               H SCH.sub.3                                                                               H H H  H  H   5  173-176                                   81   S Ph                                                                               H                                                                                 ##STR16##                                                                              Cl                                                                               H H  H  H  46  247-250                                   82   S Ph                                                                               H                                                                                 ##STR17##                                                                              H H H  H  H  50  150-152                                   __________________________________________________________________________

Example A83

N-Methyl-phenoxy-4-pyrrolyacridone

1.3 g (4 mmol) of 4-aminoN-methyl-1-phenoxyacridone and 0.8 g (6 mmol) of 2,5-dimethoxytetrahydrofuran are heated at 130° C. for 30 minutes in 10 ml of glacial acetic acid. The reaction mixture is then poured into 100 ml of water, and the product is extracted with toluene/tetrahydrofuran. The organic phase is washed successively with saturated aqueous socium bicarbonate solution, water and saturated aqueous sodium chloride solution, dried using sodium sulfate and evaporated. Purification by column chromatogrpahy (silica gel, ether/hexane 1:1) and subsequent recrystallization from toluene/isopropanol gives the desired product. Further details are given in Table 3.

Examples A84-A86

The compounds of Examples A84-A86 are prepared analogously to Example A83, with 2,5-dimethoxytetrahydrofuran being replaced in Example A85 by 2,3-dimethylsuccinic anhydride and in Example A86 by dimethylmaleic anhydride. Further details are given in Table 3.

                                      TABLE 3                                      __________________________________________________________________________     Example                            Yield                                                                              Melting                                 No. A                                                                               X   R R.sub.6                                                                          R.sub.7                                                                          R.sub.8  R.sub.9                                                                          R.sub.10                                                                          R.sub.11                                                                          R.sub.12                                                                          (%) point (°C.)                      __________________________________________________________________________     83   NCH.sub.3                                                                          Ph                                                                               H H                                                                                 ##STR18##                                                                              H H  H  H  87  177-180                                 84   S   Ph                                                                               H H                                                                                 ##STR19##                                                                              H H  H  H  64  164-166                                 85   NCH.sub.3                                                                          Ph                                                                               H H                                                                                 ##STR20##                                                                              H H  H  H  85  221-223                                 86   NCH.sub.3                                                                          Ph                                                                               H H                                                                                 ##STR21##                                                                              H H  H  H  79  248-249                                 __________________________________________________________________________

Example A87

4-Acetlyamino-N-methyl-1-pheonzyacridone

1.3 ml (16 mmol) pyridine and 0.28 ml (4 mmol) of acetyl chloride are added to a solution of 0.7 g (2 mmol) of 4-amino-N-methyl-1-phenoxyacridone in 20 ml of chloroform, and the mixture is stirred at room temperature for 6 hours. The solution is washed with hydrochloric acid (18%), water and saturated aqueous sodium chloride solution, dried using sodium sulphate and evaporated. The residue is washed with diethyl ether and filtered off. Yield: 0.6 g (83%) melting point: 252°-254° C.

Example A88 and A89

The following are obtained in an analogous manner to that in Example A87:

A88: 4-(2Ethylhexanoylamino)-N-methyl-1-phenoxyacridone, melting point 154°-156° C., yield 70%.

A89: 4-(3-Chloro-2,2-dimethylpropionylamino)-N-methyl-1-phenoxyacridone, melting point: 217°-218° C., yield: 80%.

Example A90

2,4-Dichloro-1-phenoxythioxanthone sulfoxide

A colution of 3 g (8 mmol) of 2,4-dichloro-1-phenoxythioxanthone and 0.9 g (8 mmol) of H₂ O₂ (30%) in 100 ml of glacial acetic acid is refluxed for 1 hour. The mixture is subsequently poured into 250 ml of water and extracted with 150 ml of toluene. The organic phase is washed with water, aqueous sodium bicarbonate solution (10%) and saturated aqueous sodium chloride solution, dired using sodium sulfate and evaporated. The residue is recyrstallized from toluene/isopropanol. Yield 2.1 g (67%) melting point: 207°-209° C.

Example A91

2,4-Dichloro-1-phenoxythioxanthone sulfodioxide

If the reaction is carried out using 2.7 g of H₂ O₂ (24 mmol) 30%) and the product is purified by column chromatography (silica gel, CH₂ Cl₂), 3.26 g (74%) of the sulfone are obtained; melting point: 197°-198° C.

Example A92

1-(3',5'-Dichlorophenoxy)-3-(α-cyclobenzyl)thioxanthone

2 g (4.9 mmol) of 1-(3',5'-dichlorophenoxy)-3-chlorothioxianthone, 0.86 g of benzyl cyanide, 2.03 g of potassium carbonate and 20 ml of DMSO are stirred at 80° C. for 6 hours. The mixture is discharged into 2N HCl/tetrahydrofuran/toluene, and the organic phase is separated off, dried over sodium sulfate and evaportaed. Chromatography on silica gel using methylene chloride gives 0.72 g (30%) of product, melting point 145°-155° C.

Example A93

1-(3',5'-Dichlorophenoxy)-3-benzoylthioxanthone

0.3 g (0.61 mmol) of the compound of Example A92 is stirred at 60° C. with 130 mg (0.92 mmol) of potassium carbonate and 5 ml of DMSO. Air is passed into the mixture for 6 hours at 60° C. The mixture is worked up as in Example A92, and the crude product is recrystallized from methylene chloride/pentane. Yield 0.20 g (69%), melting point 160°-163° C.

Example A94

1Phenoxythioxanthone 3,4-N-butylimide

3.0 g (7.8 mmol) of 1-nitrothioxanthone 3,4-N-butylimide, 0.89 g (9.4 mmol) of phenol, 2.16 g (15.7 mmol) of potassium carbonate and 30 ml of DMSO are stirred at 25° C. for 2 hours. The mixture is discharged into 2N HCl/methylene chloride. The organic phase is separated off, dried over sodium sulfate and evaporated. Recrystallization from methylene chloride/pentane gives 2.88 g (86%) of product of melting point 198°-199° C.

Examples A95 and A96

The following compounds are obtained analogously to Example A94, using the appropriate phenols:

A95: 1-(3,5-Dichlorophenoxy)thioxanthone 3,4-N-butylmide, melting point 207°-213° C., yield 81%.

A96: 1-(2-Methoxy-4-formylphenoxy)thioxanthone 3,4-N-butylimide, melting point 260°-263° C., yield 78%.

Example A97

2,4-Dichloro-1-(3-hydroxyphenyl)-N-methylacridone

8 g (25.6 mmol) of N-methyl-1,2,4-trichloroacridone, 8.46 g (76.8 mmol) of resorcinol, 14.15 g (102.4 mmol) of potassium carbonate and 80 ml of NMP are stirred at 60° C. for 30 hours. The mixture is discharged into water/tetrahydrofuran/toluene. The organic phase is washed with water, dried over sodium sulfate, filtered through silica gel and evaporated. The residue is chromatographed on silica gel using methylene chloride. The fractions containing the product are evaporated, and the residue is recrystallized from o-dichlorobenzene. Yield: 5.45 g (55%), melting point 220°-222° C.

B) USE EXAMPLES Example B1

1.8 g of the compound from Example A6 are dissolved in 60 mg of methyl methacrylate, and 3.6 mg of azobisisobutyronitrile are added. Using a syringe, with exclusion of air, the solution is transferred into a cell comprising two glass plates with a PVC tube of external diameter 3 mm as spacer. After 18 hours at 70° C. in a circulation oven, the method methacrylate has polymerized completely. The clear plate obtained in this way is cut into strips and employed for exposure experiments. On exposure under a mask using a 5000 W mercury high-pressure lamp at a distance of 80 cm, a dark blue negative image of the mask is obtained.

Examples B2-B5

Colour change systems as light indicators, photosensitizers and photoinitiators

Solutions comprising 100 g of technical grade epoxide-cresol novolak (epoxide value 4.5 eq/kg), 50 g of a tecnical grade bisphenol A diglycidyl ether (epoxide value 0.35 eq/kg), 30 g of Ultramix talc (cyprus), 180 g of cyclohexanone, 5×10⁻³ mol of the compounds according to the invention listed in Table 4, and 4 g of (η⁶ -cumene)(η⁵ -cyclopentadienyl)iron(II) trifluoromethanesulfonate are applied to a circuit board using a wire doctor blade. The initially wet film is dried at 80° C. Exposure of the plates produced in this way is carried out using a 5000 watt mercury high-pressure lamp at a distance of 50 cm from teh superimposed mask (Stouffer wedge). The exposure time is 1 minute. The plate is then pre-cured at 110° C. for 10 minutes. The development is carried out in cyclohexanone, the unexposed areas (solder eyes) being dissolved. The plates are then post-cured at 135° C. for 30 minutes. The plates obtained in this way are dipped into a solder bath (270° C.) for 10 seconds, during which no changes are observed.

The colour changes and the final wedge step of the Stouffer wedge (FWS) to be imaged are shown in Table 4.

                  TABLE 4                                                          ______________________________________                                                  Compound                                                              Example  from                                                                  No.      Example      Colour change                                                                               FWS                                         ______________________________________                                         B2       A69          Colourless/cyan                                                                              7                                          B3       A70          Colourless/violet                                                                            8                                          B4       A7           Colourless/violet                                                                           10                                          B5       A93          Colourless/green                                                                            10                                          ______________________________________                                    

Examples B6-B74

The suitability of these materials is tested in two formulations of photosensitive offset plate coatings:

Formulation I contains only the compounds according to the invention and no additional sensitizer.

It comprises:

1) 2.50 g of a copolymer comprising 86 parts by weight of 6-(dimethylmaleinimidyl)hex-1-yl methacrylate and 14 parts by weight of methacrylic acid (40% by weight in methoxypropanol), M_(w) :100000

2) 5.00 ml of the comound according to the invention (1% by weight in dimethylformamide)

3) 0.50 ml of Rhodamine B (dye), 1% by weight in ethylcellulose

4) 2.50 ml of ethyl glycol acetate.

Formulation II contains, in addition to the compounds according to the invention, an additional, commercially available sensitizer.

1) 2.50 g as in formulation I

2) 2.50 ml of the compound according to the invention (2% by weight in dimethylformamide)

3) 2.50 ml of dioctyl 3,4-thioxanthonedicarboxylate, 2% by weight in dimethylformamide

4) 0.50 ml of Rhodamine B, 1% by weight in ethylcellulose

5) 2.50 ml of ethyl glycol acetate

The formulations are applied to an offset plate substrate, i.e. aluminium sheet which has been electrolytically roughened and anodized, by spin coating (30 seconds at 500 rpm), and dried at 80° C. for 15 minutes, giving a coating weight of 1.1-1.5 g/m². The coating is then exposed through a Stouffer wedge (increments of optical density O.D.=0.15) using a 2000 watt metal halide lamp for 100 seconds (distance 75 cm from the vacuum frame). Development is carried out manually at 20° C. by gentle rubbing for 45 seconds with a wad soaked in the following developer solution:

75.0 g of sodium metasilicate pentahydrate

0.4 g of wetting agent (Supronic B 50, ABM Chemicals Ltd.)

925.0 g of demineralized water.

The plates are briefly rinsed with tap water and allowed to dry, and the photosensitivity is then assessed by determining the final wedge step of the numbered Stouffer wedge (FWS) to be imaged. The more wedge steps imaged at a certain exposure energy, the higher the photosensitivity of the coating.

Virtually all the formulations used here give offset printing plates of high photosensitivity and good abrasion resistance, which permits large print runs.

The results are shown in Table 5. The quality of the colour change directly after exposure is given a grade:

1=image poorly visible

2=image readily visible

3=image very readily visible.

The duration in time of the image (image stability) was also assessed by carrying out a qualitative check after 1 hour and after 24 hours for any fading of the image.

                                      TABLE 5                                      __________________________________________________________________________     Compound    Formulation I      Formulation II                                  Example                                                                             from              Image stability    Image stability                      No.  Example No.                                                                           FWS                                                                               Colour change                                                                          (h)     FWS                                                                               Colour change                                                                          (h)                                  __________________________________________________________________________     B6   A92    10 3        1      10 3        1                                   B7   A9     7  2       24      9  2       24                                   B8   A67    5  1       24      8  1       24                                   B9   A95    10 3       24      10 3       24                                   B10  A68    7  1       24      9  1       24                                   B11  A69    7  1       24      8  1       24                                   B12  A70    6  1       24      8  1       24                                   B13  A71    9  2       24      9  2       24                                   B14  A92    11 2       24      9  2       24                                   B15  A66    7  1       24      10 1       24                                   B16  A78    9  2       24      9  2       24                                   B17  A79    7  2       24      9  2       24                                   B18  A80    3  1       24      7  1       24                                   B19  A73    6  1       24      9  2       24                                   B20  A74    5  2       24      9  2       24                                   B21  A35    8  2       24      10 2       24                                   B22  A36    7  1       24      10 1       24                                   B23  A37    7  2       24      9  2       24                                   B24  A38    7  2       24      9  2       24                                   B25  A39    6  2       24      9  2       24                                   B26  A40    6  2       24      9  2       24                                   B27  A41    6  2       24      8  2       24                                   B28  A42    0  1       24      7  1       24                                   B29  A43    0  1       24      5  1       24                                   B30  A44    7  2       24      9  2       24                                   B31  A45    6  2       24      8  2       24                                   B32  A46    6  2       24      8  2       24                                   B33  A47    7  2       24      8  2       24                                   B34  A48    7  2       24      9  2       24                                   B35  A49    8  2       24      9  2       24                                   B36  A6     8  3       24      9  3       24                                   B37  A34    4  1        1      7  1        1                                   B38  A33    6  2       24      8  2       24                                   B39  A84    6  1       24      8  1       24                                   B40  A34    9  2       24      9  2       24                                   B41  A50    6  2       24      8  2       24                                   B42  A51    8  2       24      10 2       24                                   B43  A52    7  2       24      8  2       24                                   B44  A53    5  2       24      8  2       24                                   B45  A54    6  2       24      7  2       24                                   B46  A58    7  2       24      9  2       24                                   B47  A59    8  2       24      9  2       24                                   B48  A55    6  2       24      7  2       24                                   B49  A57    8  2       24      8  2       24                                   B50  A60    6  2       24      8  2       24                                   B51  A61    6  2       24      9  2       24                                   B52  A62    7  2       24      8  2       24                                   B53  A63    0  2       24      6  2       24                                   B54  A64    4  1       24      7  1       24                                   B55  A12    9  2       24      9  2       24                                   B56  A13    8  2       24      9  2       24                                   B57  A14    5  2       24      8  2       24                                   B58  A15    6  2       24      8  2       24                                   B59  A16    9  2       24      9  2       24                                   B60  A17    5  2       24      8  2       24                                   B61  A18    8  3       24      9  3       24                                   B62  A19    7  2       24      9  2       24                                   B63  A20    8  2       24      9  2       24                                   B64  A21    5  2       24      8  2       24                                   B65  A22    8  2       24      9  2       24                                   B66  A23    9  2       24      9  2       24                                   B67  A24    7  2       24      9  2       24                                   B68  A25    5  2       24      8  2       24                                   B69  A26    8  3       24      8  3       24                                   B70  A27    4  2       24      7  2       24                                   B71  A85    8  3       24      9  3       24                                   B72  A29    9  3       24      10 3       24                                   B73  A97    6  2       24      8  2       24                                   B74  A30    9  3       24      10 3       24                                   __________________________________________________________________________ 

What is claimed is:
 1. A compound of the formula I ##STR22## in which X is O, S, SO, SO₂ or NR₁₃,R₁ to R₅, independently of one another, are H, C₁ -C ₁₂ alkyl, C₁ -C₁₂ alkoxy, C₁ -C₁₂ alkylthio, C₁ -C₄ alkyl--SO--, C₁ -C₄ alkyl--SO₂ --, halogen, CF₃, --CN, --NO₂, --OH, --COOR₁₄, --CON(R₁₅)₂, or --N(R₁₅)₂, or the radical of the formula ##STR23## in which R₁₆ and R₁₇, independently of one another, are C₁ -C₆ alkyl, phenyl, C₁ -C₆ alkylphenyl or (C₁ -C₆ alkyl)₂ -phenyl, or R₃ and R₄ or R₄ and R₅, in each case together, are --CH═CH--CH═CH--, R₆ to R₁₂, independently of one another, are H, C₁ -C₁₂ alkyl, C₁ -C₁₂ alkoxy, C₁ -C₁₂ alkylthio, C₁ -C₁₂ alkyl--SO--, C₁ -C₁₂ alkyl--SO₂ --, benzyl or C₁ -C₄₆ alk-1-yl which is 1-substituted by a total of one or two --CN and/or --COOR₁₄, phenyl, phenyl--C₁ -C₄ alkylene, phenyl--CO--, phenyloxy, phenylthio, phenyl--SO--, pnenyl--SO₂ --, benzyloxy, benzylthio, benzyl--SO--, benzyl--SO₂ --, C₁ -C₁₈ acyl--O--, --COOR₁₄, --CON(R₁₅)₂, C₁ -C₁₈ acyl--NR₁₅ --, (R.sub. 15)₂ N--, halogen, --CF₃ or --CN, or each two adjacent racicals of R₆ to R₁₂ are the groups --CO--O--CO-- or --CO--NR₁₃ --CO-- the pheynyl radicals and radicals containing pnehyl groups being unsubstituted or substituted by halogen, --CN, --CF₃, C₁ -C₆ alkylthio, C₁ -C₆ alkoxy, C₁ -C₆ alkyl, --COOR₁₄, --CO--N(R₁₅)₂ or C₁ -C₁₂ acyl--O--, R₁₃ is H, C₁ -C₁₂ alkyl or C₁ -C₁₂ acyl, phenyl or benzyl, which are unsubstituted or substituted by C₁ -C₆ alkyl, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, halogen or --COOR₁₄, the two R₁₅ together are C₄ -C₈ alkylene, 3-oxa-1,5-pentylene, 3-thia-1,5-pentylene, 1.3-butadiene-1,4-diyl or 2-aza-1,3-butadiene-1,4-diyl, or the R₁₅ radicals, independently of one another, are H, C₁ -C₁₂ alkyl, or phenyl or benzyl which is unsubstituted or substituted by C₁ -C₆ alkyl, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, halogen or --COOR₁₄, and R₁₄ is phenyl, (C₁ -C₄ alkyl)phenyl, benzyl, 1-phenyleth-2-yl, benzyl or 1-phenyleth-2-yl substituted by 1 or 2 C₁ -C₁₂ -alkyl, C₁ -C₂₀ -alkyl, C₃ -C₈ -cycloalkyl, C₃ -C₈ -cycloalkylmethyl, or a polyoxaalkylene radical of the formula --(C_(n) H_(n2) --O--)_(m) R₁₈, in which n is an integer from 2 to 4, m is a number from 1 to 12, and R₁₈ is C₁ -C₁₈ -alkyl, C₃₄ -C₈ -cycloalkyl, C₅ - or C₆ -cycloalkylmethyl, phenyl, benzyl, or phenyl or benzyl, substituted by 1 or 2 alkyl groups having 1 to 12 carbon atoms, with the exception of 1-phenoxy-4-methylxanthen-9-one.
 2. A compound according to claim 1, in which, in the formula I, R₁ to R₅, independently of one another, are H, C₁ -C₆ alkyl, C₁ -C₆ alkoxy, halogen, --CF₃, --CN, --NO₂, --COOR₁₄, --OH, or --N(R₁₅)₂, or R₃ and R₄ or R₄ and R₅, in each case together, are --CH═CH--CH═CH--, each R₁₅ is C₁ -C₆ alkyl, and R₁₄ is linear or branched C₁ -C₁₈ alkyl.
 3. A compound according to claim 2, in which, in the formula I, at least 2 of the radicals R₁ to R₅ are H.
 4. A compound according to claim 1, in which in the formula IR₆ to R₁₂, independently of one another, are H, C₁ -C₆ alkyl, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, C₁ -C₆ alkyl--SO--, C₁ -C₆ alkyl--SO₂, C₁ - or C₂ alkyl which is 1-substituted by a total of one or 2 --CN and/or COOR₁₄, phenyl, phenyl-C₁ -C₄ alkylene, phenyl--CO--, phenyloxy, phenylthio, phenyl--SO--, phenyl--SO₂ --, benzyloxy, benzylthio, benzyl--SO--, benzyl--SO₂ --, C₁ -C₈ acyl--NR₁₅ --, --COOR₁₄, --CON(R₁₅ ₂, (R₁₅)₂ N--, --F, --Cl, --Br, --CF₃ or --CN or each two adjacent R₆ to R₁₂ radicals together are --CO--O--CO-- or CO--NR₁₃ --CO--, R₁₃ is C₁ -C₆ alkyl, or phenyl or benzyl which are unsubstituted or substituted by C₁ -C₄ alkyl, C₁ -C₄ alkoxy, F, Cl, Br or --COOR₁₄, R₁₄ is H, linear or branched C₁ -C₁₈ alkyl, phenyl, benzyl or --C_(n) H_(2n) --O_(m) R₁₈, where cyclohexyl, phenyl or benzyl, and R₁₅ is C₁ -C₆ alkyl, or phenyl or benzyl which is unsubstituted or substituted by C₁ -C₄ alkyl, C₁ -C₄ alkoxy, --F, --Cl, --Br or --COOR₁₄, or the two R₁₅ radicals together are 1,4-butylene, 1.5-pentylene, 3-oxa-1,5-pentylene or 1,3-butadiene-1,4-diyl.
 5. A compound according to claim 1, in which, in the formula I at least two of the radicals R₆ to R₁₂ are H.
 6. A compound according to claim 1, in which, in the formula I, R₆ is H, --Cl, --Br or methyl.
 7. A compound according to claim 1, in which, in the formula I, R₉ is H or --Cl.
 8. A compound according to claim 1, in which, in the formula I, R₁ is H or --Cl.
 9. A compound according to claim 1, in which, in the formula I, R₁₀ and/or R₁₂ is --Cl, --Br, unsubstituted or substituted phenoxy or --COO--(C₁ -C₁₂ alkyl).
 10. A compound according to claim 1, in which, in the formula I, R₆ is H, --Cl, --Br or methyl, or in which, in the formula I, R₉ is H or --Cl, or in which, in the formula I, R₁₁ is H or --Cl, or in which, in the formula I, R₁₀ and/or R₁₂ is --Cl, --Br, unsubstituted or substituted phenoxy or --COO--(C₁ -C₁₂ alkyl), or in which, in the formula I, R₇ and/or R₈ is H, --F, --Cl, --NO₂, --CR₃, --Br, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, phenyl--CO--,α-cyanobenzyl, C₁ -C₈ acyl--NR₁₅ --, pyrryl, --COO--(C₁ -C₁₂ alkyl), or phenoxy, phenylthio or phenylsulfonyl, which are unsubstituted or substituted by --F, --Cl, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, --COOH or --COO--(C₁ -C₁₂ alkyl), or R₇ and R₈ together are ##STR24## and R₁₃ is H or C₁ -C₆ alkyl.
 11. A compound according to claim 1, in which, in the formula I, R₁₃ is C₁ -C₄ alkyl or C₁ -C₈ acyl, or phenyl or benzyl which are unsubstituted or substituted by F or --COOR₁₄, and R₁₄ is H or C₁ -C₁₂ alkyl.
 12. A compound according to claim 1, in which, in the formula I, R₁₄ is H, C₁ -C₁₈ alkyl, --C_(n) H_(2n) --O_(m) H, phenyl, C₁ -C₆ alkylphenyl, benzyl, C₁ -C₆ alkylbenzyl or cyclohexyl, n is an integer from 1 to 6, and m is a number from 1 to
 20. 13. A compound according to claim 1, in which, in the formula I, R₁₅ is H, C₁ -C₆ alkyl, phenyl, benzyl, or the two R₁₅ radicals together are tetramethylene, pentamethylene, 3-oxa-1,5-pentylene or 1,3-butadiene-1,4-diyl.
 14. A compound according to claim 1, in which R₁ to r₅ are H or R₁, r₂, R₄ and R₅ are H and R₃ is --CO₂ C₂ H₅, R₆ and R₈ are Cl, and R₇ and R₉ -R₁₂ are H and R₃ is --CO₂ C₂ H₅, R₆ and R₈ are Cl, and R₇ and R₉ -R₁₂ are H, and X is NCH₃ or N-n-C₃ H₇.
 15. The compound according to claim 9, wherein X is O, each of R₁ to R₆ and R₈ to R₁₁ are H, and R₇ and R₁₂ are phenoxy. 